Nematodes for leatherjackets - treat every year?

[quanglewangle]

We had a serious leatherjacket attack on our formal ornamental lawn three years back. Nearly Roundup'ed and rotavatored it to start again. Someone put us on to nematodes: while not an instant solution they have worked.

Question is : now lawn is back OK (not wonderful but OK) do I apply nematodes every year just in case?

[burnie]

As the Crane fly will be laying eggs again around now, I am guessing you will have to, I don't know as I have never has the desire to have a lawn that required that much work.
Leatherjackets in the Lawn & How to Control Them | Online Turf
Leatherjackets / RHS Gardening